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Summary: Increased glycolytic metabolism recently emerged as an essential process driving host defense against Mycobacterium tuberculosis (Mtb), but little is known about how this process is regulated during infection. Here, we observe repression of host glycolysis in Mtb-infected macrophages, which is dependent on sustained upregulation of anti-inflammatory microRNA-21 (miR-21) by proliferating mycobacteria. The dampening of glycolysis by miR-21 is mediated through targeting of phosphofructokinase muscle (PFK-M) isoform at the committed step of glycolysis, which facilitates bacterial growth by limiting pro-inflammatory mediators, chiefly interleukin-1β (IL-1β). Unlike other glycolytic genes, PFK-M expression and activity is repressed during Mtb infection through miR-21-mediated regulation, while other less-active isoenzymes dominate. Notably, interferon-γ (IFN-γ), which drives Mtb host defense, inhibits miR-21 expression, forcing an isoenzyme switch in the PFK complex, augmenting PFK-M expression and macrophage glycolysis. These findings place the targeting of PFK-M by miR-21 as a key node controlling macrophage immunometabolic function. : Hackett et al. identify a role for the anti-inflammatory miR-21 in limiting host glycolysis during tuberculosis (TB) infection to favor bacterial replication. This occurs by targeting a pro-glycolytic isoform at the rate-limiting step in glycolysis, PFK-M, a process antagonized by the host Th1-cytokine IFN-γ, to promote full macrophage activation and antimicrobial function. Keywords: macrophage, metabolic reprogramming, tuberculosis, mycobacterium tuberculosis, glycolysis, microRNA, miR-21, interleukin-1b, phosphofructokinase, interferon gamma

Summary: Neutrophil granule proteases are thought to function as anti-microbial effectors, cooperatively hydrolyzing microorganisms within phagosomes, or upon deployment into the extracellular space. However, evidence also suggests that neutrophil proteases play an important role in the coordination and escalation of inflammatory reactions, but how this is achieved has been obscure. IL-1 family cytokines are important initiators of inflammation and are typically released via necrosis but require proteolytic processing for activation. Here, we show that proteases liberated from activated neutrophils can positively or negatively regulate the activity of six IL-1 family cytokines (IL-1α, IL-1β, IL-33, IL-36α, IL-36β, and IL-36γ) with exquisite sensitivity. In contrast, extracellular neutrophil proteases displayed very poor bactericidal activity, exhibiting 100-fold greater potency toward cytokine processing than bacterial killing. Thus, in addition to their classical role as phagocytes, neutrophils play an important immunoregulatory role through deployment of their granule proteases into the extracellular space to process multiple IL-1 family cytokines. : Here, Clancy et al. show that proteases released by activated neutrophils into the extracellular space exhibited poor antimicrobial activity but were potent modulators of IL-1α, IL-1β, IL-33, IL-36α, IL-36β, and IL-36γ activation states. Thus, neutrophils play a key role in modulating inflammatory responses through processing of multiple IL-1 family cytokines. Keywords: IL-1 family, inflammation, IL-33, IL-36, neutrophil, cathepsin G, elastase, cell death, necrosis, microbial killing